This application claims priority to European Application No. 00 870 292.0, filed Dec. 6, 2000, the disclosure of which is herein incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a guide vane stage of a compressor, comprising a succession of guide vane or stator stages separated by rotor stages of rotating vanes, each guide vane stage consisting of fixed vanes connecting an inner ring to an outer ring.
2. Description of the Related Art
Coaxial compressors are well known per Se, and are used in several types of applications. In particular, they are used in twin-structure engines, turbofan engines and turbojet engines. It is also noted that they are present in power stations. These low-pressure or high-pressure compressors substantially consist of several rotating vane stages or rotor stages separated by stator stages or guide vane stages whose function is to reposition (rectify) the speed vector of the fluid exiting the previous stage before sending it to the next compartment.
Each of these guide vane stages consists essentially of fixed vanes connecting an outer ring to an inner ring, both of which are concentric.
A major problem in the case of the guide vane stages of a compressor is that said vanes should be securely fastened to the rings in a particularly efficient manner. Specifically, this fastening of the vanes to the rings must be optimal so as to be able to withstand accidents such as the breaking of a vane or the ingestion of a foreign body such as a bird into said turbojet engine.
Usually, the vanes are fastened to the rings, both the inner and outer rings, by means of rivets, bolts or welds. Nevertheless, the use of these means of fastening has the major drawback of disrupting the flow and of generating a loss of pressure in the aerodynamic stream.
U.S. Pat. No. 2,812,159 discloses a device for assembling vanes comprising a series of U-shaped components, each of said vanes being provided with a hole at the bottom of the xe2x80x9cUxe2x80x9d which fits the free end of said vanes, said assembling being secured by means of fastening means comprising among other things screws and which are adapted so as to prevent lateral and axial movements of the vanes. However, disruption of the aerodynamic flow stream is encountered when screws or similar fastening means are used.
It has also been proposed in British Patent No. A-732 919 to use a device for assembling the vanes, wherein the vanes are assembled together by means of a sheet metal skin through the vanes and used as a supporting structure passing and by means of a flange. Moreover, end portions of the vanes are drilled to provide holes through which a locking wire extends circumferentially of the assembly, so that the vanes are retained in position. A tack-weld may be provided between the flange and the vanes so as to ensure an additional retention of the vanes. The problem of the disruption of the aerodynamic flow stream is therefore still existing.
French Patent No. A-1 252 179 is related to an assembly of fixed vanes on rings, wherein said fixed vanes are transiently linked together by their T-shaped feet by means of a strip which fits to the top of said feet. However, even if it is not necessary to remove thereafter said strip, said assembly still uses screws to fasten the vanes to the rings, with thus has the same drawbacks as the one mentioned hereabove.
U.S. Patent No. 5,569,019 discloses a fan stator assembly comprising inner and outer shrouds provided with openings through which vanes pass, said vanes being radially restrained to the inner and outer shrouds by means of seals. Each vane substantially consists of two parts, an airfoil section and a foot. The vanes preferably comprise a non-metallic composite material consisting of a plurality of compression molded, heat cured plies, including plies of para-aramid fibers which are continuous throughout the airfoil section and the foot of the vanes but are discontinuous (cut) at the junction of the airfoil section with the foot.
U.S. Patent No. 2,812,158 discloses a stator ring assembly for a turbocompressor, comprising an outer ring, an inner ring and rows of stator vanes, wherein the outer end of each vane is received in an opening in the outer ring and projects beyond said outer ring. In said assembly, two rows of vanes are held in position by means of a circumferentially stressed band surrounding and separate from the outer ring and engaging with the outer end surfaces of the vanes.
The present invention aims to propose a solution for simplifying the assembly of vanes fixed both to the inner ring and to the outer ring.
In particular, the present invention aims to provide a solution which offers great simplicity of assembly and which requires no additional assembly operations.
The present invention aims also to propose a solution which allows the aerodynamic flow stream not to be affected by the presence of welds or rivets on the ring.
The present invention aims also to provide an inexpensive solution.
The present invention relates to a guide vane stage of a compressor comprising two rings, an inner ring and an outer ring, both of which are concentric and preferably circular and connected to each other via a series of fixed vanes. At least one of the rings, and preferably both the inner and outer ring, are provided with holes which allow said vanes to pass through these holes to allow them to be fastened to the rings. With this aim, the vanes also have, at at least one end and preferably at both of their ends, an aperture to allow a locking element to pass through. This locking element will advantageously make it possible to securely fasten the vanes to at least one and preferably to both the rings on the non-functional side, that is to say on the side of the inner face for the inner ring and on the side of the outer face for the outer ring.
According to the present invention, the vanes are securely fastened to the ring or rings by passing a tape in one or more pieces, which successively passes through all the apertures of the vanes on the same guide vane stage, on the non-functional side of the rings.
Advantageously, this tape has an elastic function and will be buried in an elastomeric element which allows the various components, and in particular the locking elements, to be protected.